1. Field of the Invention
The present invention relates to a toner discharge mechanism, a toner cartridge, and an image forming apparatus using the toner cartridge.
2. Description of the Related Art
A developing device using a two-component developer is structured such that, when a toner in the developing device has been consumed and reduced by image forming, a toner cartridge supplies the toner to the developing device so as to prevent a concentration of the toner of the developer from being less than or equal to a predetermined value.
For example, a toner cartridge is known which includes: a toner storage section for storing a toner to be supplied; a toner discharge outlet through which the toner is discharged toward a developing device; and a toner conveying screw (auger screw) for conveying the toner from the toner storage section to the toner discharge outlet (see, for example, Japanese Unexamined Patent Application No. 2006-235255).
Further, another toner discharge device is also known which includes: a toner conveying path formed in a cylindrical shape; an auger screw which is rotatably mounted in the toner conveying path, and a toner discharge outlet on a lowermost stream side in a toner conveying direction, wherein the auger screw includes a reversed helical blade (reversed spiral) on the lowermost stream side (see, for example, Japanese Unexamined Patent Application No. 2008-32769).
However, in a toner cartridge which allows a toner to be discharged through the toner discharge outlet by using the auger screw, a fluidity of the toner may be reduced due to, for example, the toner cartridge having been transported over a long distance or the toner cartridge having being left unused for a long period of time. Therefore, when driving of the auger screw is recommenced, the toner stored in the vicinity of the toner discharge outlet is not smoothly discharged through the toner discharge outlet. The toner which is accumulated on an inner wall surface (a wall surface for bearing the auger screw) in the lowermost stream portion of the toner cartridge, and the toner pushed to the downstream side in the toner conveying direction by the rotation of the auger screw cannot move anywhere, and are tightly packed, so that the auger screw stops rotating (by locking phenomenon).
Further, the use of the auger screw including the reversed helical blade on the lowermost stream side can prevent the toner from being accumulated on a surface (a wall surface for bearing the auger screw) in the lowermost stream portion of the toner cartridge. However, once the toner stored in the vicinity of the toner discharge outlet cannot be smoothly discharged through the toner discharge outlet, the toner pushed in the toner conveying downstream direction by the rotation of the auger screw, and the toner pushed back due to the opposite spiral by the rotation of the auger screw, hit against each other at one point. Therefore, a pressure rapidly rises, and the toner is tightly packed, resulting in occurrence of the locking phenomenon. That is, the problem that the locking phenomenon of the auger screw occurs is not solved.